Observed (filled red circles) and synthetic spectra (continuous lines) around the HF(1-0) R9 line for the star NGC 6397 #73589. The black line corresponds to a synthetic spectrum computed for the atmospheric parameters of this star reported in Table 1 and adopting the largest fluorine abundance ([F/Fe]  = −0.1) ever measured in any GC. The green lines correspond to synthetic HF lines for a very evolved star at the RGB tip of NGC 6397 with T_eff = 4250 K and unrealistic F enrichments for a GC, [F/Fe]  = −0.1 and +0.3 dex, respectively.